1. Technical Field
The present invention relates to an image forming apparatus and an image forming program.
2. Related Art
When forming a color image, various colors are reproduced by using color materials with colors which are basic for forming a color image (hereinafter, referred to as basic colors), for example, color materials with C (cyan) M (magenta) Y (yellow) or color materials with R (red) G (green) B (blue). In a case of using CMY as the basic colors, a color material with K (black) is additionally used, in some cases. Further, a color material with a color other than the basic colors or K (hereinafter, referred to as a “spot color”) is used, or a transparent color material is used, in some cases.
A metallic color is used as the spot color, in some cases. The metallic color is used for creating a glossy appearance or sparkle of metal. For example, JP-A-62-067558 discloses a technique to create a metallic appearance (metallic luster) such as a silver color or a gold color with an electrophotographic image forming apparatus, using metallic powder such as aluminum or brass as a color material. In addition, in JP-A-2006-050347, an image is formed so that a color material with a metallic color is disposed on a lowermost layer, and a color having a designated metallic appearance is reproduced, using a color material with a metallic color and a color material with a color other than the metallic color. Further, in JP-A-2006-317633, an image is formed so that a color material with a metallic color is disposed on an uppermost layer, and a metallic appearance (sparkle) is obtained.
In practice, if a color material is produced experimentally using a metallic pigment (aluminum), and a color material with a metallic color and a color material with the other color are superimposed onto each other to reproduce a given metallic color such as a gold color or the like, although the color material with a metallic color is disposed on an uppermost layer or a lowermost layer, the color reproduction is performed and a sparkle appearance is obtained. However, in both cases, a metallic glossy (Flop Index) obtained from the metallic spot color ink used in printing is not acquired.
FIGS. 5A and 5B are a schematic view of examples of cross sectional structures of an image formed by an image forming apparatus using a color material with a metallic color of the related art and an image printed using metallic spot color ink. In the drawing, reference numeral 21 denotes a medium, reference numeral 22 denotes a metallic pigment, and reference numeral 23 denotes a color material with a color other than a metallic color. FIG. 5A shows an example of a cross-sectional structure of an image in a case of forming an image by an electrophotographic image forming apparatus using a color material with a metallic color and a color material with the other color. In the electrophotographic image forming apparatus of the related art, the color material with a metallic color and the color material with the other color are superimposed onto each other to be formed on the medium 21 such as paper, and then, are heated and melted to be fixed. Since a thickness of a layer of the color material after the fixation is equal to or greater than a particle size of the color material with a metallic color, as shown in FIG. 5A, directions of metallic pigments 22 which are used as a color material with a metallic color are set to be uneven. Accordingly, specular directions on the surface of the metallic pigments 22 with respect to incident light are not even, and an amount of diffuse reflective light becomes relatively great, and thus, a glossy appearance is not acquired. Further, since the directions of the metallic pigments 22 are not even, surface roughness also becomes greater compared to a case of not using the color material with a metallic color. Also with this surface roughness of the image, specular reflectance is low and diffuse reflectance becomes to be high, and a glossy appearance is not acquired.
On the other hand, an example of a cross-sectional structure of an image in a case of printing using metallic spot color ink is shown in FIG. 5B. In a case of reproducing a metallic color in printing, printing is performed using metallic special color ink with a color to be reproduced. Accordingly, a thickness of an ink layer is smaller than a particle size of the metallic pigments 22 used in the metallic spot color ink, and directions of the metallic pigments 22 are restricted. Thus, orientation is high, the surface roughness of the image is small, the specular reflectance is high, and the diffuse reflectance is relatively low, compared to a case shown in FIG. 5A, and therefore a glossy appearance is acquired.
The present invention aims at providing an image forming apparatus and an image forming program which obtain a glossy appearance, even in an image in which various metallic colors are reproduced using color materials with given metallic colors and color materials with the other colors.